‘ Funny’ green cloud concerns residents
Fallout continues from collapse of tailings dam
A cloud of sediment from the collapse of the tailings dam at Imperial Metals’ Mount Polley mine extends over “many” tens of square kilometres, deep below the surface of Quesnel Lake, shows research by the University of Northern B. C.
The tailings dam failure on Aug. 4 released millions of cubic metres of water and tailings containing potentially toxic metals into Polley Lake adjacent to the mine, Hazeltine Creek and Quesnel Lake.
Residents in Likely, on the shores of Quesnel River near the mine site, have raised concerns about the cloud of sediment that appears and disappears from time to time, described as a “funny” green colour.
The B. C. government and Imperial Metals have acknowledged the plume, but UNBC’s research is the first to characterize the size of the sediment cloud.
“In a matter of a few hours, the watershed was affected at an extent never before seen, and that will possibly last for decades,” said UNBC professor Phil Owens.
The plume of sediment, typically located below 25 metres, is moving both down the lake towards the town of Likely and up the lake past Cariboo Island, UNBC’s research shows.
There is a concern that sediments from the plume could accumulate in Quesnel River but also in the deltas of rivers up the lake, including the Horsefly River, an important sockeye salmon spawning river, said Owens.
Researchers investigating the affects of the tailings dam collapse — which includes scientists from UNBC and the Department of Fisheries and Oceans — are concerned about the potential for heavy metals to accumulate up the food chain, explained Owens.
Research is beginning on microscopic zooplankton, at the bottom of the food chain, and samples are about to be sent off for testing, said Owens.
To determine the long- term implications for lake trout and salmon will probably take a couple of years, he said, adding UNBC is seeking funding for a four- to five- year study.
“It’s nice to be able to say at the moment that drinking water standards are pretty good and the plume is quite diffused. But if things concentrate down into certain focus areas such as gravel beds, which is key for the salmon and lots of different organisms, I think that could then be more of a concern,” said Owens, the research chair of land ecology at UNBC.
“We don’t know the answer to that yet,” he said.
The Quesnel Lake watershed is an important salmon spawning ground for Fraser River runs, particularly for sockeye. About one million sockeye spawn in the watershed each year.
Imperial Metals has argued the effects on the environment should not be great from the tailings, as its acidgenerating potential is neutralized by the significant amount of carbonate in the rock.
UNBC water sample analysis shows the plume comprises very fine particles with a median diameter of about one micron ( a human hair is 40 to 50 microns).
The university operates the Quesnel River Research Centre, just a few kilometres downstream of Quesnel Lake, and staff began a sampling and monitoring program the same day the tailings dam collapsed.